Terry Woods
Member
- Join Date
- Apr 2002
- Posts
- 3,170
Randy...
I'm curious as to what you have found or tried.
I'm fully aware of the problem you are describing. I went through the same problem last year.
We had a need for a new punch press with an infeed and outfeed system.
It was decided that the outfeed system would be designed and built in-house. I would design the controls at/for the outfeed and the interaction between it and the press. Not a problem... I had already done two of these and the whole outfeed process was very straight-forward.
It was also decided that the infeed system would be designed and built in-house. As with our other punches the infeed would be mechanically connected to the press cycle through a power-takeoff at the press... or so I thought.
So... "The" Mechanical Engineer from the front office was told to go "shopping" for the press.
Before I go on, I gotta tell ya about this "Engineer".
About 10-years ago the real "Mechanical Engineer (PE)" up and dies... what-a-ya gonna do? He was pretty good... sorta, now and then... His buddy, the draftsman, wasn't and still isn't among the sharper knives in the drawer. Between the two of them they were usually able to get something going... sorta.
They had two design philosophies.
The first design philosophy was the "JunkYard Wars" philosophy.
"Got a task? Go through the junk pile, find some junk... and make it work!"
In other words, they designed from the bottom-up instead of top-down. Instead of determining the best possible system and then paring back to meet the budget, they would start at the bottom with whatever junk they had, then kept adding junk to the process until something just barely worked.
Then they employed their second design philosophy:
"Make it do one cycle, then turn it over to Maintenance - they can tweak-it-in. Hey! It worked! What else ya want?"
So, as I said, "About 10-years ago the real "Mechanical Engineer (PE)" up and dies..."
ENTER, Stage-Left: The new Mechanical Engineer... the Draftsman... and he hasn't been spending any time near a honing stone.
So... "The" Mechanical Engineer from the front office was told to go "shopping" for a press. Did I tell you he was tighter than Scrooge? He is. He couldn't find a decent punch press in the junkyard so, as much as it pained him to do so, he had to go a buy one at a tradeshow.
He bought one for $75,000. It pained him to do so, but he felt a little better because he decided that "We doan need no steekin' power-takeoff! We can synchronize the press and infeed electrically... that's what Terry is for!"
He was absolutely giddy about having "...done it on the cheap!". He "saved" $2,500.
I always know (now) when I'm in for grief... he slips into a cheap-movie German accent (cheap - what else).
When I first heard about it I blew a gasket! I said, "Forget about it! That's the worst possible method you could have decided on, especially since the mechanical linkage is so reliable! It's always in sync while running AND at Start-Up! Now get the damned Power-takeoff. He said it doesn't have one nor does it have any provisions for one. (The punch was not on site yet). Ba$tard!
Cutting to the quick...
I developed a bunch of code... I soon became intrigued with the possibilities... ABB Drives are pretty damned flexible! (programming-wise) ...the press arrived. It has provisions for a takeoff. Ba$tard!
He still refuses to buy the takeoff, "It will take too long to get it and besides, we're already too deep into this electrical takeoff".... he says. Ba$tard!
I used the Punch Press Flywheel as the reference. Take a look on a 'scope at a power supply with poor filtering. The trace shows the same pattern produced by flywheel speed on a press. The speed is not constant. There's just a slight dip in speed as the punch goes through the material. So, that was my reference - had to be so. I had no "resolver-type" information to work with - only some programmable cam-points. Also, this is a mechanical press - clutch driven.
So, now I'm trying to sync one cycle on the infeed with one cycle on the punch.
Cutting even quicker to the quick... (It's too long of a story.)
While running, the infeeder was synchronized beautifully with the punch. Start-Up was a different matter. If the press and indexer were synchronized while running, I couldn't get them to synchronize on Start-Up. So I worked on getting Start-Up synchronized. Then I was able to get Start-Up synchronized. Start-Up synchronized beautifully! However, when I got Start-Up synchronized, the system ended up too far out of bounds for the operating parameters to bring it back to stable "running" operation.
So, I could have one or the other, but not both.
Later, after the other shoe hit the floor and the damned Power-Takeoff finally showed up, I did some analysis on the index-drive and the press. The two were essentially mutually exclusive!
So, my advice, to save yourself a bunch of headaches and to get production running... "get the damned power-takeoff!"
Even if the system can be worked out without the PTO, it will still be, logically, very delicate - might work, might not.
Put aside the programming ego and go with the sure-fire method! There are plenty of other fish that a PTO can't handle.
I'm curious as to what you have found or tried.
I'm fully aware of the problem you are describing. I went through the same problem last year.
We had a need for a new punch press with an infeed and outfeed system.
It was decided that the outfeed system would be designed and built in-house. I would design the controls at/for the outfeed and the interaction between it and the press. Not a problem... I had already done two of these and the whole outfeed process was very straight-forward.
It was also decided that the infeed system would be designed and built in-house. As with our other punches the infeed would be mechanically connected to the press cycle through a power-takeoff at the press... or so I thought.
So... "The" Mechanical Engineer from the front office was told to go "shopping" for the press.
Before I go on, I gotta tell ya about this "Engineer".
About 10-years ago the real "Mechanical Engineer (PE)" up and dies... what-a-ya gonna do? He was pretty good... sorta, now and then... His buddy, the draftsman, wasn't and still isn't among the sharper knives in the drawer. Between the two of them they were usually able to get something going... sorta.
They had two design philosophies.
The first design philosophy was the "JunkYard Wars" philosophy.
"Got a task? Go through the junk pile, find some junk... and make it work!"
In other words, they designed from the bottom-up instead of top-down. Instead of determining the best possible system and then paring back to meet the budget, they would start at the bottom with whatever junk they had, then kept adding junk to the process until something just barely worked.
Then they employed their second design philosophy:
"Make it do one cycle, then turn it over to Maintenance - they can tweak-it-in. Hey! It worked! What else ya want?"
So, as I said, "About 10-years ago the real "Mechanical Engineer (PE)" up and dies..."
ENTER, Stage-Left: The new Mechanical Engineer... the Draftsman... and he hasn't been spending any time near a honing stone.
So... "The" Mechanical Engineer from the front office was told to go "shopping" for a press. Did I tell you he was tighter than Scrooge? He is. He couldn't find a decent punch press in the junkyard so, as much as it pained him to do so, he had to go a buy one at a tradeshow.
He bought one for $75,000. It pained him to do so, but he felt a little better because he decided that "We doan need no steekin' power-takeoff! We can synchronize the press and infeed electrically... that's what Terry is for!"
He was absolutely giddy about having "...done it on the cheap!". He "saved" $2,500.
I always know (now) when I'm in for grief... he slips into a cheap-movie German accent (cheap - what else).
When I first heard about it I blew a gasket! I said, "Forget about it! That's the worst possible method you could have decided on, especially since the mechanical linkage is so reliable! It's always in sync while running AND at Start-Up! Now get the damned Power-takeoff. He said it doesn't have one nor does it have any provisions for one. (The punch was not on site yet). Ba$tard!
Cutting to the quick...
I developed a bunch of code... I soon became intrigued with the possibilities... ABB Drives are pretty damned flexible! (programming-wise) ...the press arrived. It has provisions for a takeoff. Ba$tard!
He still refuses to buy the takeoff, "It will take too long to get it and besides, we're already too deep into this electrical takeoff".... he says. Ba$tard!
I used the Punch Press Flywheel as the reference. Take a look on a 'scope at a power supply with poor filtering. The trace shows the same pattern produced by flywheel speed on a press. The speed is not constant. There's just a slight dip in speed as the punch goes through the material. So, that was my reference - had to be so. I had no "resolver-type" information to work with - only some programmable cam-points. Also, this is a mechanical press - clutch driven.
So, now I'm trying to sync one cycle on the infeed with one cycle on the punch.
Cutting even quicker to the quick... (It's too long of a story.)
While running, the infeeder was synchronized beautifully with the punch. Start-Up was a different matter. If the press and indexer were synchronized while running, I couldn't get them to synchronize on Start-Up. So I worked on getting Start-Up synchronized. Then I was able to get Start-Up synchronized. Start-Up synchronized beautifully! However, when I got Start-Up synchronized, the system ended up too far out of bounds for the operating parameters to bring it back to stable "running" operation.
So, I could have one or the other, but not both.
Later, after the other shoe hit the floor and the damned Power-Takeoff finally showed up, I did some analysis on the index-drive and the press. The two were essentially mutually exclusive!
So, my advice, to save yourself a bunch of headaches and to get production running... "get the damned power-takeoff!"
Even if the system can be worked out without the PTO, it will still be, logically, very delicate - might work, might not.
Put aside the programming ego and go with the sure-fire method! There are plenty of other fish that a PTO can't handle.
